Conventional solid drawing materials are obtained by adding, if necessary, an oil such as mineral oil, a resin and the like to a compound comprising at least a wax, a pigment and an extender to adjust a hardness thereof.
Known are, for example, 1) a solid drawing material comprising at least a pigment, a resin for molding, a wax, an extender, and 0.1 to 20% by weight of a terpene resin and/or a terpene resin derivative based on the total amount of the drawing material (refer to, for example, patent document 1), 2) a solid drawing material comprising at least a pigment, an olefin base resin, a wax, a fatty acid amide, and at least one resin selected from the rosin, an ester gum, a coumarone resin and an alkyd resin (refer to, for example, patent document 2), 3) a fluorescent drawing material comprising a fluorescent pigment, waxes, a fatty acid which is a solid at room temperature and adhesive resin having a Gardner value of 4 or less (refer to, for example, patent document 3), 4) a solid drawing material containing at least a colorant, polybutene and a mixture comprising at least one selected from an ethylene-propylene-butene copolymer, amorphous polypropylene, an ethylene-polar monomer copolymer, polyethylene, polyisobutylene, and amorphous poly-α-olefin (refer to, for example, patent document 4), and 5) a solid drawing material comprising at least a colorant, a molding agent and an oil material, wherein a middle chain fatty acid is used as the oil material (refer to, for example, patent document 5).
However, the solid drawing materials described in the patent documents 1 to 5 are reduced in strength and liable to be broken when an amount of oil which is liquid is increased for softening, and therefore it is impossible to mold them into fine leads or shave the tips of the leads to sharpen them, which makes it difficult to draw fine pictures. Also, when drawing pictures on smooth and non-absorbing surfaces of art paper, coated paper, milk packs, plastics such as PET, metal, glass, white boards, and the like, a problem is involved therein in terms of that the leads slip on the surfaces thereof to make it impossible to draw dark pictures thereon in spite of the soft leads.
On the other hand, if the drawing materials are increased in an amount of the resins in order to enhance strength of the leads, the drawing materials can be molded into fine leads, but the leads are hard and therefore involve a problem in terms of that the leads cannot be used for drawing pictures on smooth and non-absorbing surfaces of art paper, coated paper, milk packs, plastics such as PET, metal, glass, white boards, and the like.
Meanwhile, recently known is a solid drawing material which is prepared by mixing a specific resin component, an organic solvent, a gelling agent and a colorant and which is improved in a coloring property on a smooth surface (refer to, for example, patent document 6), but since it contains liquid, it is still unsatisfactory in terms of strength. The drawing material cannot be molded into a fine lead, and the tip of the lead cannot be shaved and sharpened. Also, when the organic solvent having a low boiling point is used, an outer holder for preventing volatilization is required to provide a problem in terms of inferior convenience in use.
Further, the present applicants provide a solid drawing material containing a specific resin component, a wax component, a pigment, titanium dioxide and an extender, wherein the specific resin component and the wax component are mixed in a specific ratio to solve the problem described above (refer to, for example, patent document 7), but a content of the low-melting point blending component or the liquid oil is restricted to some extent in order to maintain the practical strength, and when further dark drawn lines are required, their intensity is limited. Accordingly, the drawing material concerned is desired strongly to be further improved.
Also, various inventions have so far been published as conventional water-soluble solid drawing materials, and they are actually put on the market as the products.
Known as representatives thereof are water-soluble solid drawing materials in which in the blending components of a conventional non-aqueous solid drawing material comprising a non-aqueous wax, a resin, a pigment and an extender, a surfactant or polyethylene glycol replaced the non-aqueous wax described above is used, if necessary, as a wax and in which the resin is replaced with a water-soluble resin (refer to, for example, patent documents 8 and 9).
Further, known as the water-soluble solid drawing material are, for example 1) a water-soluble solid drawing material comprising at least a colorant and a surfactant, wherein two or more kinds of surfactants having a melting point of lower than 55° C. and surfactants having a melting point of 55° C. or higher are used in combination of each one or more kinds out of both the surfactants (refer to, for example, patent document 10), 2) a water-soluble solid drawing material containing at least a pigment, a wax, a surfactant which is solid at room temperature, and phytosterol (refer to, for example, patent document 11), and 3) a water-soluble solid drawing material comprising at least a colorant, sulfonic acid-modified polyvinyl acetate and a fatty acid metal salt (refer to, for example, patent document 12).
However, when drawing pictures on smooth surfaces, the above water-soluble solid drawing materials slip on the surfaces to make it less liable to be abraded thereon, and therefore when drawing pictures on art paper, coated paper, milk packs, plastics such as PET, metal, glass, white boards, and the like, a problem is involved in terms of that the drawing materials cannot draw pictures or can only draw them unsatisfactorily.
Further, products called water-soluble crayon are put as well on the market, and all of them are softened by low-melting point substances or oils which are liquid at room-temperature. Accordingly, when drawing pictures on smooth and non-absorbing surfaces of art paper, coated paper, milk packs, plastics such as PET, metal, glass, white boards, and the like, a problem is involved therein in terms of that the crayons slip on the surfaces to make dark lines impossible to be drawn and that solubility of the crayon on a drawing surface is unsatisfactory because of water repellency of the oil.
On the other hand, conventional solid drawing materials for non-calcined color pencil leads are produced by a method in which a compound comprising a binder such as a resin, waxes, a pigment and an extender is kneaded, extrusion molded and in which the molded product is then blended, if necessary, with water, an organic solvent and the like and dried.
The non-calcined color pencil leads are desired to draw pictures more darkly in order to enhance a quality thereof, but if the leads are softened by increasing a content of the low-melting wax so that the leads are increased in abrasion on paper surfaces of drawing paper and canvases for oil paintings, the problem that the leads are liable to be broken is caused.
Also, when drawing pictures on smooth and non-absorbing surfaces of art paper, coated paper, milk packs, plastics such as PET, metal, glass, white boards, and the like, a problem is involved therein as well in terms of that the leads slip on the surfaces to make it scarcely possible to draw pictures thereon.
In conventional solid drawing materials for non-calcined color pencil leads, known are, for example 1) a non-calcined color pencil lead prepared by blending at least a binder, a colorant and an extender and molding the mixture, wherein a specific secondary amide type long chain acylamino acid and/or a salt thereof and lithium soap are used in combination (refer to, for example, patent document 13), 2) a non-calcined color pencil lead containing a colorant, a binder, an extender, a wax and/or oils & fats, and a hydrophilic surfactant, wherein a polyoxyethylene adduct of oils & fats is contained as the hydrophilic surfactant described above (refer to, for example, patent document 14), and 3) a non-calcined color pencil lead containing at least a water-soluble resin, a colorant and an extender, wherein a mixture of glycerin fatty acid ester and/or pentaerythritol fatty acid ester, each having a melting point of 65° C. or lower and rosin and/or a rosin-modified product is contained as waxes (refer to, for example, patent document 15).
However, in the non-calcined color pencil leads described in the patent documents 14 and 15, a problem is still involved therein in terms of sufficiently high strength and color developability, and when drawing pictures on smooth and non-absorbing surfaces of art paper, coated paper, milk packs, plastics such as PET, metal, glass, white boards, and the like, a problem is involved therein as well in terms of that the leads slip on the surfaces to make it scarcely possible to draw pictures thereon.
Also, the non-calcined color pencil lead disclosed in the patent document 15 described above has not so far been available, and it is strongly desired to be further improved in a drawing performance when drawing pictures on smooth and non-absorbing surfaces of metal, glass, white boards and the like.
On the other hand, conventional solid drawing materials for calcined color pencil leads are produced, in a case of a black lead, by a method in which a compound comprising a binder such as clay, a natural polymer, a synthetic polymer, pitch and asphalt, powder such as natural crystalline graphite, natural amorphous graphite, artificial graphite, carbon black and boron nitride, and, if necessary, a plasticizer, a solvent and the like is kneaded, extrusion molded, in which the molded product is then dried up, if necessary, to remove the solvent and the like, in which it is heated at a high temperature of 800° C. or higher in a non-oxidative atmosphere and in which it is further impregnated with a fat & oil such as whale oil, lard, spindle oil, liquid paraffin, an α-olefin oligomer and dimethyl silicone oil, a wax and the like.
Also, in a case of calcined color leads, they are produced by a method in which a compound comprising a binder such as clay, a natural polymer, a synthetic polymer, pitch and asphalt, boron nitride, if necessary, powder such as natural crystalline graphite, natural amorphous graphite, artificial graphite and carbon black, and additives such as a plasticizer and a solvent is kneaded, extrusion molded, in which the molded product is then heated, if necessary, to remove the solvent and the like, in which it is heated at a high temperature of 800° C. or higher in a non-oxidative atmosphere, in which it is further heated at 800° C. or lower in an ambient atmosphere, in which it is then dipped in a solution of polymetalloxane such as perhydropolysilazane, polysiloxane, polyaluminoxane and polyzirconoxane, a silicon chelate, an aluminum chelate, a zirconium chelate, and the like, and heated subsequently at a high temperature of 700° C. or higher in a non-oxidative atmosphere and in which it is then impregnated with a non-volatile dye ink and the like, and a method in which a compound comprising clay, boron nitride, if necessary, powder such as natural crystalline graphite, natural amorphous graphite, artificial graphite and carbon black, and additives such as a solvent is kneaded with water and the like, extrusion molded, in which the molded product is then heated, if necessary, to remove water, in which it is heated at a high temperature of 800° C. or higher in a non-oxidative atmosphere and in which it is further impregnated with a non-volatile dye ink and the like.
Further, in recent years, known as drawing materials providing calcined color pencil leads having a smooth writing performance and an effect of enhancing intensity are, for example, 1) a calcined pencil lead in which pores are impregnated with at least a fluorine base oil (refer to, for example, patent document 16), 2) a calcined pencil lead in which pores provided in a calcined lead body are impregnated with at least a specific polyethylene glycol monostearate and/or a specific polyethylene glycol distearate (refer to, for example, patent document 17), and 3) a calcined pencil lead in which pores provided in a calcined lead body are impregnated with an ink comprising at least polyethylene glycol and 12-hydroxystearic acid (refer to, for example, patent document 18).
However, the conventional calcined pencil leads described in the patent documents 16 to 18 have been improved so that both the black leads and the color leads can draw dark lines on ordinary wood free paper, copier paper and the like, but when drawing pictures on smooth and non-absorbing surfaces of art paper, coated paper, plastics, metal, glass, white boards, and the like, a problem is involved therein in terms of that the leads slip on the surfaces to make it scarcely possible to draw pictures thereon, and even when drawing pictures on paper of a notebook, a memo pad and the like having a slightly high smoothness, a problem is involved therein in terms of that the leads slip on the surfaces to provide only light drawn lines.